Many modern radio receivers provide "seek" and "scan" features which are respectively initiated by depression of seek and scan buttons. In response to a request for either of these features, the radio receiver searches for the next station signal that meets certain criteria. In the case of a "seek" request, the receiver terminates the search when a suitable station signal is found; and in the case of "scan" request, the receiver temporarily locks on a station signal that meets the criteria to permit a listener to preview the current program. The listener can terminate the scan by again depressing the scan button. If the listener does not terminate the scan, the receiver searches and locks onto candidate station signals for short preview periods of time and terminates the scan when the end of the frequency band is reached.
Prior art Stop on Station (SOS) circuits use essentially received field strength to determine if a received radio (station) signal is acceptable for listening or not. These prior art SOS circuits which evaluate the field strength of received station signals are generally termed "AGC" for Automatic Gain Control. Since received signal strength may vary substantially within short periods of time, prior art SOS circuits may stop on radio station signals which are inadequate for good listening or may pass over signals which are in fact acceptable for listening. Variation in received signal strength is typically more noticeable in automobile radios than home receivers.